Low-fibre diet linked to leaky gut: Mouse study

A lack of dietary fibre leads to a rapid increase in gut permeability and changes in microbiota composition in mice, says a new study in Cell Host & Microbe.

Mice fed with a low-fibre, Western Style Diet (WSD) for 8 weeks developed increased gut permeability compared with their littermates fed a standard (control) chow diet, found researchers from the University of Gothenburg.

The WSD fed mice also displayed a lower rate of gut mucous growth than the control group. Increased permeability of the mucous layer and the reduced growth rate began to occur in as little as three days after starting the WSD feeding.

The scientists also found that the above changes were accompanied by an alteration in the gut bacteria make-up.

"Low-fibre diets alter bacterial composition and influence what they produce," ​commented study director Professor Gunnar Hansson. "The result can be greater penetrability that affects the body's cells.​

"We clearly illustrated the rapid process by which the mucus layer responds to dietary modifications and subsequent bacterial changes,"​ he added.

Increased Proteobacteria​

Among the most notable changes in microbiota composition was an increase in numbers of Proteobacteria – a type of bacteria that has previously been linked with inflammation.

The high abundance of Proteobacteria was due to a bloom of the pathogenic genus Helicobacter. ​

Additionally, WSD fed mice suffered a rapid decrease in the proportion of fibre-degrading bacteria Bifidobacterium. ​The amount of short-chain fatty acids (SCFAs), a fermentation product of fibre, was also found to be lower in the mice on the WSD. This finding strongly suggests that the lowered Bifidobacterium ​abundance was due to the lack of fibre in the diet, the researchers noted.

Prebiotics/ probiotics reverse damage ​

Damage to the gut mucosa was reversed by supplementation of either the prebiotic fibre inulin, or the probiotic Bifidobacterium longum. ​However, the scientists found that the two supplements had distinct effects.

Inulin repaired the gut permeability, but did not improve the mucous growth rate. Conversely, B. longum ​supplementation increased mucous growth, but had no effect on permeability.

In order to clarify whether the altered gut microbiota caused the slower mucous growth and increased permeability, the researchers transplanted gut bacteria from the chow-fed mice into the WSD-fed animals. The faecal transplant fully restored the mucous growth and significantly reduced the gut permeability.

Significance​

Previous research has identified possible links between low-fibre diets and inflammatory bowel disease in humans. The findings of this study, if translatable to humans, may enable future strategies for protecting the gut mucosa, suggested the researchers.

“Modern diets such as WSD increase the risk for developing inflammatory bowel diseases in humans and, providing the existence of a similar diet-microbiota-mucous axis, it may be possible to design improved probiotic and prebiotic options for treating conditions that involve defects in the colonic mucous layer,”​ they concluded.